This invention relates to a method for use in producing light metal alloys, in particular aluminum alloys with elements which are commonly known to be alloyable to aluminum, as for instance Mg, Si, Fe, Mn etc. In this method a melt is vacuum treated and alloyed and at the same time the content impurities therein, such as sodium, hydrogen, oxides and other non-metallic particles, are effectively reduced. At the same time the melt can also be grain refined. The invention also comprises an apparatus for carrying out the method.
In recent years there has been in the aluminum market a steadily increasing demand for high speed extrudable alloys and rolling alloys, including a number of special alloys having particular requirements, for instance alloys with qualities such as high brilliancy after anodizing, the latter alloy being among others characterized by a low content of iron.
When producing aluminum alloys for casting in the form of "quarter finished products" as for instance direct chilled cast rolling ingots, extrusion billets and wire ingots, the actual alloying work compared to the production of plain aluminum, i.e. aluminum alloyed with only Fe and Si, involves reduced productivity and capacity with melt treatment methods being now employed.
Another disadvantage with this alloy production is that the alloying elements are usually introduced into the melt, which is stirred by hand or mechanically, by means of various tools which then contaminate the melt (confer the properties of the various materials or metals to the aluminum melt).
In the aluminum industry there is a further requirement for purifying or refining the raw metal, depending upon the fields of use for which the same is intended. In particular it is necessary in many instances to reduce the contents of sodium, finely dispersed oxide and other non-metallic particles from the aluminum melt at the same time as hydrogen is degased from the melt. In the production of several alloys it is absolutely necessary to carry out such purification.